ZIF-67@Se@MnO₂: A Novel Co-MOF-Based Composite Cathode for Lithium–Selenium Batteries

In this study, metal organic frameworks (MOFs) are prepared as a support to tether active selenium through melt-diffused method, in which MnO2 nanoparticles are loaded on the surface of a Co-MOF (ZIF-67) through simple postmodification means. Selenium is uniformly dispersed on the surface of ZIF-67, and MnO2 nanoparticles (∼5 nm in diameter) are coated on the surface of Se. As an analogue of sandwich, the MOF@Se@metal-oxide structure can inhibit the shuttle effect and dissolution of polyselenides in the electrolyte, which is confirmed by the cyclic voltammetry, galvanostatic discharge/charge, and electrochemical impedance tests. In addition, the cathode displays an excellent electrochemical performance. Especially, the discharge capacity of the ZIF-67@Se@MnO2 cathode is 329 mA h g–1 after 100 cycles at 1C (C = 675 mA g–1) with the high capacity retention of 83.7%. Furthermore, the ZIF-67@Se@MnO2 cathode displays stable capacities of 273 and 232 mA h g–1 after 100 cycles at 2C and 5C, respectively